Hi, English isn’t my mother tongue so I was asking myself that question since I first encounted a w/… Back then I was like: “What tf does ‘w slash’ stand for?” And when I found out I was like “How, why, and is it any intuitive?” But I never dared to ask that until now
I’m just adding an additional source, because I just recently read about this way of using the forward slash to create abbreviations. English Language & Usage has a good post on Stackexchange. Wikipedia says they are used for “two-letter initialisms” (a type of abbreviation). Wikipedia also provides some more examples, see here.
Oh, thanks a lot for that input :D